Coupler with waveguide transition for an antenna in a radar-based level measurement system

Abstract

A mechanism for coupling a coaxial waveguide to another waveguide. The mechanism includes a lower or matching waveguide and an impedance transformer. A coaxial port couples the coaxial waveguide to the matching waveguide. The matching waveguide has a waveguide impedance which is close to the impedance of the coaxial waveguide. This arrangement allows matching between the coaxial waveguide and the matching waveguide over a wider frequency band. The impedance transformer couples the matching waveguide to the other waveguide. The impedance transformer comprises a single-stage, double-stage, or multi-stage transformer. The mechanism is suitable for coupling an antenna to a coaxial cable interface in a radar or microwave based level measurement or time of flight ranging systems.

Description

FIELD OF THE INVENTION [0001] The present invention relates radar-based level measurement systems, and more particularly to a coupler with a waveguide transition mechanism suitable for rod antenna and horn antenna applications, and other waveguide-based antennas such as slotted waveguides. BACKGROUND OF THE INVENTION [0002] Time of flight ranging systems find use in level measurements applications, and referred to as level measurement systems. Level measurement systems determine the distance to a reflective surface (i.e. reflector) by measuring how long after transmission energy, an echo is received. Such systems may utilize ultrasonic pulses, pulse radar signals, or other microwave energy signals. [0003] Pulse radar and microwave-based level measurement systems are typically preferred in applications where the atmosphere in the container or vessel is subject to large temperature changes, high humidity, dust and other types of conditions which can affect propagation. To provide a su...

AI Technical Summary

Benefits of technology

[0010] In another aspect, the present invention provides a level measurement apparatus for determining a level measurement for material contained in a vessel, the level measurement apparatus comprises: an antenna; a controller having a receiver module and a transmitter module, the controller has a bidirectional port for connecting to one end of a coaxial waveguide; a coupler having a coaxial port for receiving the other end of the coaxial waveguide and coupling the coaxial waveguide to the antenna; the coupler includes a transition mechanism for transferring the electromagnetic energy between the coaxial waveguide and the antenna, the transition mechanism includes an impedance transformer and a matching waveguide, the matching waveguide is coupled to the coaxial port, and the matching waveguide has an impedance approximately matching the impedance of the coaxial waveguide, the impedance transformer has a first port for receiving the matching waveguide, a second port for coupling to the antenna, and a transition section, the transition section serves to substantially match the impedance of the antenna with the impedance of the matching waveguide; the coupler further includes a stepped section, the stepped section receives the impedance transformer, and the transition section in the impedance transformer has one or more waveguide transitions, and the stepped section of the coupler has one or more steps corresponding to the waveguide transitions; the antenna is responsive to electromagnetic signals received

Problems solved by technology

If there are losses or signal degradation in the transition between the coaxial waveguide and the antenna waveguide, then radar performance is affected.

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